Mems microphone package structure having a non-planar substrate

ABSTRACT

A MEMS microphone package structure having a non-planar substrate is provided. It includes a non-planar substrate, a lid and a transducer. The non-planar substrate includes a bearing base and a peripheral wall connecting to the bearing base. The lid is covered and connected to the non-planar substrate to form a cavity, and at least one solder pad is disposed on an outer surface of the lid or the non-planar substrate. The transducer is disposed in the cavity. A sound hole is provided to correspond to the transducer, and the sound hole is disposed at the non-planar substrate or the lid.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation in part of U.S. patent application Ser. No. 14/448,461 filed on Jul. 31, 2014 entitled “MEMS MICROPHONE PACKAGE STRUCTURE HAVING NON-PLANAR SUBSTRATE AND METHOD OF MANUFACTURING SAME”, the content of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to MEMS microphone technology, and more particularly, to a MEMS microphone package structure having a non-planar substrate that has a peripheral wall upwardly extended from a periphery of a top surface of said bearing base to maintain the overall structural strength, enabling the MEMS microphone package structure have a low profile characteristic.

2. Description of the Related Art

Compared to conventional microphones, MEMS microphones have compact size, power and price advantages, and therefore, MEMS (Micro-electromechanical Systems) microphones have been widely used in mobile phones and other electronic products. A conventional MEMS microphone package structure 70, as shown in FIG. 1, generally comprises a substrate 71, an acoustic wave transducer 72 and an application-specific integrated circuit 73 (ASIC) arranged on the substrate 71 and electrically coupled together, a plurality of electric connection structures 76 mounted in the substrate 71 for electrically connecting the application-specific integrated circuit 73 to external devices, a back cover 74 covered on the substrate 71 for protecting the internal components of the microphone. As illustrated in FIG. 1, the substrate 71 of the MEMS microphone package structure 70 bears the pressure of the acoustic wave transducer 72 and the application-specific integrated circuit 73. Therefore, in consideration of the structural strength, the substrate 71 must have a certain thickness. This factor is unfavorable to the low profile trend of the development of today's electro-acoustic products. For making a MEMS microphone package structure 70 having a low profile characteristic, subject to restriction of the internal components, the volume of the cavity 75 of the microphone is minimized. Thus, reducing the thickness of the substrate 71 is helpful to extend the volume of the cavity 75 and to enhance the acoustic performance of receiving sensitivity and signal to noise ratio of the microphone.

Further, US 2014/0037115A1 discloses a MEMS assembly. As illustrated in FIG. 2, the MEMS assembly is a three-layer structure which including a lid 102, a wall 104 and a base 106. The lid 102 has an acoustic port or opening 112. The MEMS apparatus, referenced by 108, and the IC, referenced by 110, are mounted at the lid 102. A solder region 160 is defined on a top and a bottom surface of the wall 104. The solder region is covered by solder material such that the wall 102 can be physically and electrically connected to the lid 102 and the base 106.

According to the aforesaid patent, the base 106 also needs to bear the pressure given by the lid 102, the MEMS apparatus 108, the IC 110 and the wall portion 104, and thus, the base 106 cannot be made too thin. Further, because the wall portion 104 uses solder material to electrically connect the lid 102 and the base 106, in the conventional packaging process, it needs to coat the top surface of the wall portion 104 with the solder material, reverse the wall portion 104, and then to coat the opposing bottom surface of the wall portion 104 with the solder material after reversed the wall portion 104. After the coating process, the positioning and connection of the wall portion 104 and the base 106 can then be performed. This packaging process is complicated and its cost is high. The structural strength of the soldered MEMS assembly is still low and easy to break.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is an object of the present invention to provide a MEMS microphone package structure, which can increase the volume of the cavity of the microphone without changing its external dimension and, which provides protection against electromagnetic interference.

To achieve this and other objects of the invention, a MEMS microphone package structure is provided to comprise a non-planar substrate, a lid, an acoustic wave transducer, an application-specific integrated circuit, and at least one solder pad. The at least one solder pad is mounted at the top side of the lid or the outer surface of the non-planar substrate. The non-planar substrate is a laminated structure of multiple printed circuit boards, comprising a first metal layer, a base, and a peripheral wall that extends from the base around the border thereof. Thus, the lid can be covered on the non-planar substrate and connected to the peripheral wall, defining with the non-planar substrate a cavity. Further, the acoustic wave transducer is mounted in the cavity. Further, a sound hole is selectively formed in the non-planar substrate or the lid.

Thus, the peripheral wall reinforces the overall structural strength of the non-planar substrate so that the bearing base of the non-planar substrate can be designed relatively thinner to provide a low profile characteristic, and the volume of the cavity of the microphone can be maximized without changing the external dimension of the MEMS microphone package structure

Other and further benefits, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a conventional MEMS microphone package structure.

FIG. 2 is a sectional view of a MEMS microphone package structure in accordance with a first embodiment of the present invention.

FIG. 3 is a sectional view of a MEMS microphone package structure in accordance with a second embodiment of the present invention.

FIG. 4 is a MEMS microphone package structure manufacturing flow chart of the invention.

FIG. 5 is a sectional view of a MEMS microphone package structure in accordance with a third embodiment of the present invention.

FIG. 6 is another sectional view of the MEMS microphone package structure in accordance with a third embodiment of the present invention, illustrating an alternate form of the lid.

FIG. 7 is still another sectional view of the MEMS microphone package structure in accordance with the third embodiment of the present invention, illustrating another alternate form of the lid.

FIG. 8 is a sectional view of a MEMS microphone package structure in accordance with a fourth embodiment of the present invention.

FIG. 9 is a sectional view of a MEMS microphone package structure in accordance with a fifth embodiment of the present invention.

FIG. 10 is a sectional view of a MEMS microphone package structure in accordance with a sixth embodiment of the present invention.

FIG. 11 is an elevational view of the non-planar substrate of the MEMS microphone package structure in accordance with the sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

For better understanding of the benefits, advantages and features of the present invention, a MEMS (micro-electromechanical system) microphone package structure having a non-planar substrate in accordance with a first embodiment is described herein after with reference to FIG. 2. As illustrated, the MEMS microphone package structure 1 comprises a non-planar substrate 10, a lid 20, and an acoustic wave transducer 30. The structural details of these component parts and their relative relationship are described hereinafter.

The non-planar substrate 10 is a multilayer printed circuit board with a cavity (Cavity PCB), having multiple circuit layers (not shown) and insulation layers (not shown) continuously laminated thereon and pressed and adhered in integrity to exhibit a U-shaped configuration by means of the implementation of a PCB manufacturing process. The non-planar substrate 10 comprises a bearing base 11 and a peripheral wall 12. The peripheral wall 12 is made in one piece and it is surrounded and upwardly extended from a periphery of a top surface of the bearing base 11. Further, wiring electrodes 15 and metal bumps 17 are respectively arranged on opposing top and bottom surfaces of the bearing base 11. The bearing base 11 has a sound hole 13 located therein for the passing of acoustic waves. The bearing base 11 has a plurality of electric connection structures 18, such as metal wirings and blind via holes (BVH), arranged therein for conducting the metal bumps 17 and the wiring electrode 15, so that the MEMS microphone package structure 1 can be electrically connected with external devices via the metal bumps 17. The peripheral wall 12 has an electrical conduction path formed therein, which is a first metal layer 14 formed via blind hole, plating or copper plughole techniques. In this embodiment, the first metal layer 14 is embedded in the peripheral wall 12. The peripheral wall 12 has a metal bump 16 arranged on a top surface thereof and electrically connected with the first metal layer 14. The non-planar substrate 10 may be made integrally from the material, including but not limited to glass substrate (e.g. FR-4), plastic substrate (e.g. LCP), or ceramic substrate.

The lid 20 is a flat panel member made of an insulative material (such as plastics) and includes a second metal layer 21 arranged on a bottom surface thereof. The lid 20 is covered on the non-planar substrate 10 and connected with the peripheral wall 12 so that the lid 20 and the non-planar substrate 10 define therebetween a cavity 26. After connecting the lid 20 and the non-planar substrate 10, the second metal layer 21 is electrically connected to the first metal layer 14 through the metal bump 16 at the top surface of the peripheral wall 12, so that the non-planar substrate 10 can be grounded to provide an electromagnetic shielding structure 50, thus, the first metal layer 14 and the second metal layer 21 can fully shield the microphone against electromagnetic interference.

It's worth mentioning that the lid 20 can be a metal member electrically connected to the first metal layer 14 alternatively, thereby achieving the desired electromagnetic interference shielding effect. In the present disclosure, the first metal layer 14 is adapted for grounding (i.e., works as a part of the grounded conductive path). In one or more embodiments described below, two first metal layers 14 may be provided, and selectively adapted for inputting or outputting electrical signals of internal devices in the MEMS microphone package structure 1 (to work as a part of the signal transmission path). Further, the structure of the first metal layer 14 is not limited to the design of the above-described “layered structure”, it may be of other design, such as silicon via structure.

The acoustic wave transducer 30 is bonded to the top surface of the bearing base 11 and disposed inside the cavity 26 corresponding to the sound hole 13. An application-specific integrated circuit (ASIC) 40 is bonded to the top surface of the bearing base 11 and disposed inside the cavity 26 between the acoustic wave transducer 30 and the peripheral wall 12. The acoustic wave transducer 30 is electrically connected to the application-specific integrated circuit 40 by wire bonding. Further, the application-specific integrated circuit 40 is electrically connected with the wiring electrodes 15 at the top surface of the bearing base 11 by wire bonding.

In application, the structure of the peripheral wall 12 enhances the overall strength of the non-planar substrate 10. When compared to conventional MEMS microphone package structures, the bearing base 11 of the non-planar substrate 10 can be designed relatively thinner, enabling the MEMS microphone package structure 1 to have a low profile characteristic, increasing the volume of the cavity 26 to enhance the acoustic performance of receiving sensitivity and signal to noise ratio of the microphone without changing the external dimension of the MEMS microphone package structure 1. Further, forming the peripheral wall 12 on the bearing base 11 in integration greatly enhances the overall strength of the non-planar substrate 10. The electrical conduction path can be directly formed in the one-piece non-planar substrate 10, eliminating the drawbacks of the complicated conventional multi-layer PCB manufacturing process that needs to make holes in each layer and then bond the multiple layers together.

FIG. 3 illustrates an alternative MEMS microphone package structure in accordance with a second embodiment. This second embodiment is substantially similar to the aforesaid first embodiment with one of the difference that a part of the first metal layer 14 is plated on the inner surface of the peripheral wall 12 by electroplating. Similarly, the first metal layer 14 has a metal bump 16 located at a top side thereof and electrically connected with the second metal layer 21. Further, the bottom end of the first metal layer 14 is electrically connected to the bearing base 11. Thus, the bearing base 11 has low profile and electromagnetic interference shielding characteristics.

Further, the invention has the advantage of ease of mass production. The fabrication of the MEMS microphone package structure in accordance with the present disclosure is described hereinafter with reference to the manufacturing flow chart of FIG. 4.

At first, perform Step S1: Prepare a non-planar substrate strip of an array of non-planar substrates 10 and a lid strip of an array of lids 20, wherein each non-planar substrate 10 comprises a bearing base 11, a peripheral wall 12 surrounded and extended from a top surface of the bearing base 11 along a periphery thereof, a first metal layer 14 located at the peripheral wall 12 and a sound hole 13 formed at the bearing base 11 or lid 20. It is to be noted that, in Step S1, the design of the peripheral wall 12 enhances the structural strength of the respective non-planar substrate 10, so that a large area non-planar substrate strip can be made, avoiding warping, enhancing process efficiency and reducing costs.

Thereafter, proceed to Step S2: Mount an acoustic wave transducer 30 and a application-specific integrated circuit 40 at the bearing base 11 of each non-planar substrate 10 to make each acoustic wave transducer 30 disposed above the associating sound hole 13, and then employ a wire bonding technique to electrically connect each acoustic wave transducer 30 to the respective application-specific integrated circuit 40 and also to electrically connect each application-specific integrated circuits 40 to the respective bearing base 11.

It is to be noted that, as an alternate form of the invention, the application-specific integrated circuit 40 may be arranged on the surface of the lid 20.

At final, proceed to Step S3: Connect the lid strip to the non-planar substrate strip to make each first metal layer 14 electrically connected with the respective lid 20, and then employ a singulation process to separate the material thus processed into individual MEMS microphone package structure 1.

FIG. 5 illustrates a MEMS microphone package structure in accordance with a third embodiment. In this third embodiment, in addition to one first metal layer 14 a, the peripheral wall 12 of the non-planar substrate 10 has another first metal layer 14 b mounted therein in a juxtaposed manner and electrically connected to the acoustic wave transducer 30 and the application-specific integrated circuit 40.

Further, the lid 20 is a metal substrate comprising an insulation layer 22, a metal base material 23 and an insulation layer 22 laminated together. The number of layers of the metal base material 23 may be increased according to requirements but not limited to the configuration of this embodiment. Alternatively, the structure of the metal substrate may be formed of a metal base material 23, and insulation layer 22 and a metal base material 23 using lamination. Through-silicon vias 24 are formed in the peripheral area of the lid 20 that is bonded to the peripheral wall 12 of the non-planar substrate 10, and electrically connected to solder pads 25 at the top surface of the lid 20. Thus, after connection between the lid 20 and the peripheral wall 12 of the non-planar substrate 10, the first metal layer 14 a is electrically connected to the metal base material 23 through the through-silicon vias 28, creating an electromagnetic shielding structure 50 to protect the acoustic wave transducer 30 and the application-specific integrated circuit 40 against electromagnetic interference. Further, the transmission of the input and output signals of the MEMS microphone package structure can be achieved by means of electrically connecting the first metal layer 14 b, the through-silicon vias 24 and the solder pads 25.

When compared to conventional microphone package designs, the invention reinforces the strength of the structure between the bearing base 11 and the peripheral wall 12, allowing the first metal layer 14 a and each first metal layer 14 b to be directly formed in the peripheral wall 12. Thus, the present disclosure is suitable for the implementation of the non-planar substrate strip manufacturing process, simplifying the fabrication of the MEMS microphone package structure 1 and reducing the average unit cost. Further, because the structural strength of the non-planar substrate 10 is greatly enhanced, the bearing base 11 can be made relatively thinner, enabling the volume of the cavity 26 to be maximized.

Further, during fabrication of the MEMS microphone package structure 1, it is not necessary to reverse the non-planar substrate strip; the acoustic wave transducer 30 and the application-specific integrated circuit 40 can be directly soldered or wire-bonded to the bearing base 11, simplifying the fabrication and reducing the possibility of overflow of solder to the sound hole 13. Further, forming the sound hole 13 in the bearing base 11 is helpful to improvement of the sensitivity of the MEMS microphone package structure 1 and optimization of frequency response in the super wide band.

Further, the lid 20 may be made of fiberglass substrate or ceramic substrate, as illustrated in FIG. 6 and FIG. 7. In FIG. 6, the insulation layers 22 of the lid 20 are respectively formed of a fiberglass substrate and arranged on opposing top and bottom surface of a conductive layer 27 that is made of a copper foil. The conductive layer 27 is electrically connected with the first metal layer 14 a through the through-silicon vias 28, forming an electromagnetic shielding structure. In FIG. 7, the insulation layer 22 at the top side of the conductive layer 27 (copper foil) is formed of a ceramic substrate, and the insulation layer 22 at the bottom side of the conductive layer 27 (copper foil) is made from polypropylene (PP).

FIG. 8 illustrates a MEMS microphone package structure in accordance with a fourth embodiment. Unlike the aforesaid third embodiment, the application-specific integrated circuit 40 is embedded in the bearing base 11 using a semiconductor manufacturing process, enabling signals to be transmitted to the solder pads 25 through the first metal layer 14 b and the through-silicon vias 24 and also increasing the volume of the cavity 26. Further, the first metal layer 14 a can be electrically connected to the conductive layer 27 through the through-silicon vias 28, forming an electromagnetic shielding structure 50.

FIG. 9 illustrates a MEMS microphone package structure in accordance with a fifth embodiment. In the fifth embodiment, the acoustic wave transducer 30, the application-specific integrated circuit 40 and the sound hole 13 are located at the lid 20, and electrically connected to the solder pads 25 at the bearing base 11 through the electric connection structure 29 of the lid 20 and the first metal layer 14 b of the peripheral wall 12, simplifying the circuit layout of the non-planar substrate 10, contributing to the thinning of the bearing base 11, and reducing the electrical wiring cost of the non-planar substrate 10.

FIGS. 10 and 11 illustrate a MEMS microphone package structure in accordance with a sixth embodiment. In the sixth embodiment, an annular third metal layer 19 is formed on the inner four surfaces of the peripheral wall 12 of the non-planar substrate 10 by, for example, electroplating. The third metal layer 19 is electrically connected to the second metal layer 21 of the lid 20 to constitute a grounded conductive path. Further, the peripheral wall 12 has embedded therein a plurality of first metal layers 14 a,14 b of via hole design. The first metal layers 14 a are located at the four corners of the peripheral wall 12 for electrically connecting to the second metal layer 21 of the lid 20. The first metal layers 14 b are formed in the peripheral wall 12 at other locations and adapted to work as a signal transmission path, so that the input and/or output signals of the MEMS microphone package structure 1 can be transmitted through the first metal layer 14 b and the solder pads 25 of the non-planar substrate 10.

It is to be noted that, in the sixth embodiment the first metal layer 14 a and the third metal layer 19 are both used to constitute a grounded conductive path, effectively protecting the MEMS microphone package structure 1 against interference of external electromagnetic noises.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. 

What is claimed is:
 1. A MEMS microphone package structure having a non-planar substrate, comprising: a non-planar substrate comprising a multiple layers of printed circuit boards laminated together, said non-planar substrate comprising at least one first metal layer, a bearing base and a peripheral wall being surrounded and upwardly extended from a periphery of a top surface of said bearing base; a lid covered on said non-planar substrate and connected to said peripheral wall to define a cavity; a sound hole formed at said non-planar substrate or said lid; an acoustic wave transducer mounted in said cavity; an application-specific integrated circuit electrically connected with said acoustic wave transducer; and at least one solder pad mounted at an outer surface of said lid or said non-planar substrate.
 2. The MEMS microphone package structure as claimed in claim 1, wherein said at least one first metal layer extends from said peripheral wall of said non-planar substrate to a bottom of said non-planar substrate.
 3. The MEMS microphone package structure as claimed in claim 1, wherein said lid is formed of at least one insulation layer and at least one second metal layer by lamination; said at least one second metal layer is electrically connected to said at least one first metal layer.
 4. The MEMS microphone package structure as claimed in claim 3, wherein said lid is selected from the material group of metal substrate, fiberglass substrate and ceramic substrate.
 5. The MEMS microphone package structure as claimed in claim 3, wherein said lid comprises two insulation layers and one second metal layer laminated between said two insulation layers, and said two insulation layers are made of different insulation materials respectively.
 6. The MEMS microphone package structure as claimed in claim 3, wherein said at least one second metal layer is arranged at a surface of at least one said insulation layer.
 7. The MEMS microphone package structure as claimed in claim 1, wherein said at least one solder pad and said sound hole are respectively disposed at said lid and said non-planar substrate.
 8. The MEMS microphone package structure as claimed in claim 7, wherein said at least one solder pad is electrically connected to said application-specific integrated circuit through said first metal layer.
 9. The MEMS microphone package structure as claimed in claim 7, wherein said at least one solder pad and said sound hole are both disposed at said lid or said non-planar substrate.
 10. The MEMS microphone package structure as claimed in claim 1, wherein said lid further comprises at least one via hole electrically connected to said at least one solder pad and said at least one first metal layer.
 11. The MEMS microphone package structure as claimed in claim 1, wherein said at least one first metal layer comprises at least two first metal layers adapted to work as a signal transmission path and/or a grounded conductive path.
 12. The MEMS microphone package structure as claimed in claim 11, wherein said signal transmission path is electrically connected to said application-specific integrated circuit and said at least one solder pad; said grounded conductive path is electrically connected with said lid and said non-planar substrate.
 13. The MEMS microphone package structure as claimed in claim 1, wherein said peripheral wall of said non-planar substrate is connected with said lid by at least one metal bump.
 14. The MEMS microphone package structure as claimed in claim 1, wherein said acoustic wave transducer is directly mounted on said sound hole.
 15. The MEMS microphone package structure as claimed in claim 1, wherein said application-specific integrated circuit is embedded in a bottom of said non-planar substrate.
 16. The MEMS microphone package structure as claimed in claim 14, wherein said non-planar substrate further comprises a third metal layer disposed at an inner surface of said peripheral wall.
 17. The MEMS microphone package structure as claimed in claim 16, wherein said at least one first metal layer is embedded in said peripheral wall.
 18. The MEMS microphone package structure as claimed in claim 17, wherein said third metal layer is arranged in an annular configuration.
 19. The MEMS microphone package structure as claimed in claim 17, wherein said at least one first metal layer comprises at least one first metal layer working as a signal transmission path and at least one metal layer working as a grounded conductive path. 